#include <iostream>
#include <cstring>
using namespace std;

int main(int argc, char const *argv[])
{
    string s1 = "hello";
    string s2 = "world";
    // s1.append(s2);//追加字符串
    // cout<<s1<<endl;

    // s1.assign(s2,2);
    // cout<<s1<<endl;//完全替换字符串

    s1.insert(5,"！！！");
    cout<<s1<<endl;
    cout<<s1.size()<<endl;
    cout<<s2.length()<<endl;
    return 0;
}
